Intravascular catheter with kink resistant tip

ABSTRACT

An intravascular catheter comprises a proximal portion and a distal portion. The proximal portion has greater torsional stiffness than the distal portion, while the distal portion has greater dependability than the proximal portion. In accordance with this invention the distal portion carries a helical wire support member embedded therein, the helical support member being essentially free of crossing wires, to provide kink-resistance upon bending to the distal portion.

This is a continuation of application Ser. No. 559,193 filed Jul. 27,1990 now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to an intravascular catheter which exhibitsimproved resistance to kinking in the tip even when the tip isthin-walled and flexible.

Intravascular, and particularly intravascular catheters for angioplastyor angiography are equipped with a pliable tip to facilitate theadvancement of the catheter through the vascular system of a patienttoward its objective, typically a coronary artery or a chamber of theheart. The proximal majority of the catheter length is typicallyflexible but firm, being generally equipped with a tubular, braided orotherwise crossing wire reinforcement member to provide torsionalstiffness and pushability to the catheter. Thus the catheter may bereliably rotated from the proximal end to cause the distal end to rotatea substantially equal amount.

However, the distal tip end of the catheter is desirably more flexiblethan is generally possible with such a tubular braid-reinforced cathetersection. Accordingly, in the prior art most catheters of this type carryno wire reinforcement at all at the distal tip.

Because of this, a problem arises in that, while the distal tip portionsof prior art catheters are adequately flexible and soft so thatadvancement of the catheter does not injure vascular or heart tissues,the tip portion is subject to collapsing or kinking when it is directedaround a bend in a branched blood vessel or the like. This of course isdeemed undesirable, even if the plastic material of the tip portion iscapable of springing back into uncollapsed condition when it isstraightened out again.

Accordingly, there is a need for a catheter which has a high torsionresistance in its proximal section in accordance with the prior art, butwhich exhibits a highly flexible tip which, nevertheless, hassubstantial collapse resistance, particularly resistance against kinkingas the tip is directed about a bend in a blood vessel.

In accordance with this invention, a catheter is provided which has adistal portion which may be soft and pliable as needed, but in which thedistal portion is strongly resistant to collapse so that it may bedirected through a labyrinth of branching blood vessels or the likewithout damaging tissues, but without collapsing or kinking. Theresulting catheter exhibits improved characteristics over prior artcatheters, particularly for the well-known PTCA procedure or any otherangioplasty or angiography procedure.

As a further advantage, the plastic material out of which the distalportion of the catheter of this invention can be made may be inherentlysofter than in the prior art, for added tolerability of catheteradvancement through tissues. At the same time, the distal sectionexhibits its improved and desired resistance to collapse or kinking.

DESCRIPTION OF THE INVENTION

In this invention, an intravascular catheter is provided which comprisesa proximal portion and a distal portion. The proximal portion hasgreater torsional stiffness than the distal portion. The distal portionhas greater bendability than the proximal portion.

In accordance with this invention, the distal portion carries a helicalwire support member embedded therein, which support member isessentially free of crossing wires. Thus, kink resistance is provided tothe distal portion upon bending thereof, but the distal portion remainssoft and flexible.

Preferably, the helical support member may be completely embedded in thecatheter distal portion in a manner which is analogous to prior artstructures, where complete embedding of braided wire support tubes isprovided.

It is preferred for the proximal catheter portion to carry a braidedwire tubular support member embedded therein, to provide the desiredtorsional stiffness to the catheter. The distal catheter portion of thisinvention is typically a relatively minor portion of the overall lengthof the catheter, being found primarily adjacent the tip thereof.Typically, the distal catheter portion is less than one-tenth the lengthof the overall catheter, and often only about two or three percent ofthe overall catheter length.

The embedded coils of the helical support member are preferably spacedfrom one another so that plastic material of the distal portion isolateseach of the coils from each other. This provides an improved flexibilityto the distal catheter portion, coupled with a good softness which canbe provided by the use of a plastic material that is typically softerthan the plastic material of prior art catheter distal portions.Generally, it is preferred for the distal catheter portion plasticmaterial to have a Shore "D" durometer of 25 to 50, and preferably 35 to45, compared with a similar durometer of prior art catheter tips of 60or more. This can be accomplished because of the reinforcing capabilityof the helical support member, so that a softer plastic material ma beused in the distal catheter portion, while at the same time the distalcatheter portion remains highly resistant to collapse and kinking.

The distal catheter portion may carry a distal tip that is free ofsupporting strands. Typically, such a distal tip is a relatively shortstub, typically less than 1 cm. in length, and may carry a relativelyhigh concentration of x-ray contrast medium to facilitate the x-rayvisibility of the catheter of this invention.

DESCRIPTION OF THE DRAWINGS

In the drawings, FIG. 1 is a plan view of an intravascular catheter inaccordance with this invention;

FIG. 2 is a fragmentary, plan view of a pair of coronary catheters inaccordance with this invention, showing differing designs of preformedcurves in their distal ends;

FIG. 3 is a longitudinal sectional view of part of the proximal portionof a catheter of FIG. 1;

FIG. 4 is a longitudinal sectional view of the distal portion of acatheter of FIG. 1 in accordance with this invention, in straightenedform; and

FIG. 5 is a longitudinal sectional view of a step of one manufacturingprocess of the catheter of this invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Referring to FIG. 1, a plan view of a catheter in accordance with thisinvention is disclosed. Catheter 10 defines a proximal hub 12 which maybe of conventional design, connected with a proximal portion 14, whichcomprises the majority of the length of catheter 10 and may be about 38inches long. As shown in FIG. 3, proximal portion 14 may comprisecoaxial, extruded layers including an outer layer 16 which may be madeof polyurethane, nylon, or the like, and a central layer 18 whichincludes embedded tubular woven wire braiding of conventional design forcatheters, with the nylon or other compatible plastic materialpermeating the interstices of the tubular braiding in conventionalmanner. Layers 16, 18 may be a single extrusion. Finally, an innermostlayer 20 of polytetrafluoroethylene may be provided.

Typically, the catheter of claim 1 may be sized to penetrate the smallercoronary arteries for use as a guiding catheter. Inner layer 20 may be0.0015 inch thick, while the tubular, braided layer 18 and outer layer16 may have a thickness of 0.004 inch. The entire catheter may be about100 centimeters in length, having an outer diameter of about 0.092 inchand an inner diameter of about 0.072 inch.

Catheter 10 also defines a distal portion 22, conventionally bonded tothe distal end of proximal portion 14 and typically of the same outerdiameter. A portion of distal portion 22 is shown in longitudinalsection in FIG. 4, in which it can be seen that distal portion 22comprises inner and outer coaxially positioned tubular sections. Outertubular section 24 may be of the same outer diameter as proximal section14, being made of nylon or the like. Inner tubular section 26 may besimilar to inner tubular section 2 of the proximal section, being madeof polytetrafluoroethylene, and also being of similar transversedimensions thereto.

Outer tubular section 24 carries a helical wire support member 28, whichis completely embedded within distal portion 22, as shown, with thevarious embedded coils of helical wire support member being spaced fromeach other as also shown, being separated by the plastic material oftubular section 24 such as nylon or other compatible plastic material.The wire of helical wire support member 28 may be of normally roundcross section, but, preferably, it is of rectangular cross section ofgreater width than height. This provides a strong coil while reducingthe radial depth (i.e., the thickness) of the wire cross section which,in turn, reduces the chances that the wire can be exposed to theexterior at the outer surface of distal catheter portion 22. Forexample, the helical wire may have a cross section of 0.002 inch inheight, which will be the radial direction, and 0.006 inch in width.Such a wire may be completely encapsulated in the wall of distalcatheter portion 22, even when the overall wall thickness is only about0.01 inch.

Distal portion 22, which is typically substantially about 21/2 percentof the length of proximal catheter portion 14, and is about one inch inlength. Catheter portion 22 exhibits a substantially increased softnessand resilience when compared with the softness and resilience ofproximal section 14. This is particularly provided by the fact that thehelical supporting wire 28 permits distal portion 22 to be twisted withsignificantly reduced torsion resistance when compared with the majorityof the catheter in proximal portion 14. Also, the plastic material thatmakes up outer tubular section 24 and surrounds and impregnates thehelical wire 28 may be softer than plastics that are normally used incatheters, even at their tips, being of a Shore D durometer of about 40.This is contrary to a typical plastic material used in conventionalcatheters at the tip which have a Shore D durometer on the order of 62.This substantially increased softness of the plastic material used indistal catheter portion 22 provides a portion that is very soft,resilient, and undamaging to tissues as the catheter is advanced throughthe cardiovascular system of a patient. At the same time, the presenceof supporting helical wire 28 provides an underlying strength andstability to distal portion 22 along with the softness and resilience,particularly so that the soft distal portion 22 is greatly resistant tokinking as it is distorted out of its normal, unstressed configurationas shown in FIG. 1 by the action of being forced through a convoluted,highly branched blood vessel system or the like. Distal portion 22 isfree of crossing wires, which would reduce its soft, pliablecharacteristic.

Additionally, distal catheter portion 22 can carry a tubular distal tip32, bonded to the remainder of distal portion 22, which is free of anyform of wire reinforcement. The length of such a tip may be about 0.1cm., and may be similar to the commercially available BRITE TIP (T.M.)catheter tip provided to many catheters which are marketed by the CordisCorporation. The plastic material of catheter tip 32 contains arelatively high loading of radiopaque agent, for increased x-rayvisibility of catheter tip 32.

The various components of the catheters of this invention may beconventionally bonded together in accordance with the known principlesof catheter design and manufacture.

Turning to FIG. 2, a pair of coronary catheters are shown, making use ofthe invention of this application, the catheters being in their natural,unstressed configuration. Catheter 34 illustrates a desired shape for aleft coronary catheter, with proximal portion 14a and distal portion 22being of a construction similar to that previously described. Catheter36 illustrates a desired shape for a right coronary catheter, withproximal portion 14b and distal portion 22b being of similar design tothe above as well. Both catheters may carry tips 32a and 32b of a designsimilar to tip 32 of the previous embodiment. These catheter shapesfacilitate engagement by their respective distal tips to the coronaryostium and attain the proper take off angle to provide better alignmentof the catheter and artery. This can facilitate passage of PTCAcatheters which extend through the lumen of the catheters of thisinvention and are thus properly guided into the proper locationtherethrough, as one possible use of the catheter of this invention.Alternatively, the catheter of this invention may be used in its ownright for angiography or angioplasty.

Referring to FIG. 5, a method for the manufacture of the distal catheterportion 22 is disclosed.

Using a coil winder with accurate tension and pitch control, stainlesssteel wire is coiled into the helical wire support member 28, to beprovided to distal portion 22 in accordance with this invention. Helicalwire 28 is placed about preformed polytetrafluoroethylene tubular layer26, and both are placed about pin 42. Optionally, helical member 28 mayfit into optional helical groove 40 of pin 42. Alternatively, the pin 42may be cylindrical. The size of pin 42 may be selected so that thehelically coiled wire 28, after winding, springs back into a relaxedposition that is the desired diameter of helical wire 28 in distalcatheter portion 22. Preferably, wire 28 is made of high tensilestrength spring steel.

Accordingly, coil 28 on the pin 42 may optionally be considerablysmaller than the desired, relaxed inside diameter of the coil 28 asplaced into catheter section 22. For example, to make a coil of desiredunstressed diameter of 0.08 inch, one may typically use a pin 42 havinga diameter of about 0.05 inch, although this depends on thecross-sectional dimensions of the coiled wire, its hardness, its coilingtension, and the like. Then, after release of the coil, it springs backoutwardly into the desired final dimension.

After wire 28 and tube 26 has been applied to pin 42, oversized plasticsleeve 44 is applied, which is intended to become the plastic portions16, 18 of outer tubular portion 24. Wire coil 28 may be applied to pin42 under tension to keep it to the size of the pin, typically by ascrewing action to wind the coil 28 into the grooves 40. Plastic sleeve44 is assembled over the coil, and a heat shrink tubing 46 (made forexample of polytetrafluoroethylene) is applied about plastic sleeve 44.Then, the assembly is heated at a temperature at or above the softeningpoint of plastic sleeve 44, which causes heat shrink tubing 46 to presstubing 44 forcefully against coil 28 and tube 26, and for the plastic oftubing 44 to encapsulate the coils of helical wire 28.

After the system has once again cooled, the shrink tubing 46 can beremoved by longitudinal slicing, and the composite of tubing 44, coiledwire 30, and tubing 26 can be removed by an unscrewing action from thepin 42.

Following this, the resulting product, which constitutes distal catheterportion 22, may be attached to proximal portion 14 by conventionalbonding, as a step of manufacture of the overall catheter. To obtain thebest possible outer diameter control of outer tubular portion 24, thatportion may be ground by a centerless grinding means after the step offusing plastic tubing 44 and helical wire 2 together.

Thus, by this means, a catheter is provided, typically for intravascularuse, in which the proximal portion has greater torsional stiffness thanthe distal portion, but the distal portion has greater bendability thanthe proximal portion and exhibits good kink resistance upon bending ofthe distal portion. Additionally, the distal portion may be very softand flexible despite its kink resistance, so that such a catheter iseasily advanceable through a labyrinth of blood vessels with greaterease but without damage to tissues.

The above has been offered for illustrative purposes only, and is notintended to limit the scope of the invention of this application, whichis as defined in the claims below.

We claim:
 1. An intravascular catheter which comprises a proximalportion and a distal portion, said proximal portion having greatertorsional stiffness than said distal portion, said distal portion havinggreater bendability than said proximal portion, the improvementcomprising, in combination:said distal portion defining a smooth-walledlumen and carrying a helical wire support member embedded therein, saidhelical support member being essentially free of cross wires, to providekink-resistance upon bending to said distal portion, said proximalportion carrying a braided wire tubular support member embedded therein,said catheter defining an inner, lumen-defining tubular plastic layerpositioned radially within said helical support member and a braidedwire tubular support member.
 2. The catheter of claim 1 in which saiddistal catheter portion is less than one-tenth the length of saidproximal catheter portion.
 3. The catheter of claim 1 in which saiddistal catheter portion carries a distal tip that is free of supportingstrands.
 4. The catheter of claim 1 in which said helical support memberdefines embedded coils that are spaced from each other.
 5. The catheterof claim 1 in which said distal catheter portion defines a preformedbend.
 6. The catheter of claim 1 in which said distal catheter portioncomprises a plastic material that is softer than the plastic material ofthe proximal catheter portion, said distal catheter portion plasticmaterial having a Shore "D" durometer of 25 to
 50. 7. The catheter ofclaim 1 in which the wire of said helical support member defines arectangular cross section, with the width of said wire being greaterthan the radial depth thereof.
 8. An intravascular catheter whichcomprises a proximal portion and a distal portion, said proximal portionhaving greater torsional stiffness than said distal portion and carryinga braided wire tubular support member embedded therein, said distalportion having greater bendability than said proximal portion, theimprovement comprising, in combination:said distal portion carrying ahelical wire support member completely embedded therein, said helicalsupport member being essentially free of crossing wires, to providekink-resistance upon being to said distal portion, the length of saiddistal portion being less than one tenth the length of said proximalportion.
 9. The catheter of claim 8 in which said helical support memberdefines embedded coils that are spaced from each other.
 10. The catheterof claim 9 in which said distal catheter portion comprises a plasticmaterial that is softer than the plastic material of the proximalcatheter proportion, said distal catheter portion plastic materialhaving a Shore D durometer of 35 to
 45. 11. The catheter of claim 10 inwhich said distal catheter portion defines a preformed bend.
 12. Thecatheter of claim 11 in which said distal catheter portion carries adistal tip that is free of supporting strands.
 13. The catheter of claim8 in which the wire of said helical support member defines a rectangularcross section, with the width of said wire being greater than the radialdepth thereof.
 14. An intravascular catheter which comprises:anelongated tube having a proximal portion and a distal portion; saidproximal portion extending most of the length of the catheter and havinga greater torsional stiffness than said distal portion; said distalportion defining a smooth-walled lumen and having a greater bendabilitythan said proximal portion, and comprising a softer plastic materialthan the material from which the proximal portion is formed; a helicalwire support member carried by said distal portion only, to providekink-resistance upon bending of said distal portion and to aid inproviding greater bendability than said proximal portion, the helicalwire support member defining coils, said proximal portion carrying atubular braid, said braid being completely embedded within said proximalportion and said helical wire support member being completely embeddedwithin said distal portion.
 15. An intravascular catheter as defined byclaim 14, in which said helical wire support member is free of wireextending inside of the helix, whereby a clear, open volume is providedwithin the helix to facilitate passage of PTCA catheters or the likewithin said helical wire support member.
 16. An intravascular catheteras defined by claim 14, in which said distal portion comprises an innertubular member, said helical wire support member being carried by saidinner tubular member and positioned outside of said inner tubularmember, and an outer tubular section embedding said helical wire supportmember therein.
 17. The intravascular catheter of claim 14 in which saidcoils are spaced from each other.
 18. An intravascular catheter whichcomprises:an elongated tube having a proximal portion and a distalportion; said proximal portion extending most of the length of thecatheter and having a greater torsional stiffness than said distalportion; said distal portion having a greater bendability than saidproximal portion; a helical wire support member completely embeddedwithin said distal portion only to provide kink-resistance upon bendingof said distal portion and to aid in providing greater bendability thansaid proximal portion, said distal portion, in its natural, unstressedconfiguration, being curved where said helical wire support member iscarried; said proximal portion carrying a braided wire tubular supportmember embedded therein.
 19. The intravascular catheter of claim 18 inwhich said distal portion is less than one tenth the length of saidproximal portion.
 20. The intravascular catheter of claim 18 in whichsaid helical wire support member has coils spaced from each other. 21.The catheter of claim 18 in which said distal portion comprises aplastic material having a shore "D" durometer of 25 to 50, while saidproximal portion comprises a stiffer plastic material.
 22. The catheterof claim 14 in which the wire of said helical support member defines arectangular cross section, with the width of said wire being greaterthan the radial depth thereof.
 23. The catheter of claim 22 in whichsaid distal catheter portion carries a distal tip that is free ofsupporting strands.
 24. The catheter of claim 23 in which said distalcatheter portion defines a preformed bend.